The present invention relates to oxy-fuel burners for use in high temperature furnaces, for example glass furnaces.
Air-fuel fired regenerative glass furnaces are well-known. Regenerative glass furnaces have multiple air-fuel regenerator ports for producing combustion flames for glass melting. Basic design features of glass furnaces are described in various references, for example “Glass Furnaces, Design Construction and Operation,” by Wolfgang Trier, translated by K. L. Loewenstein, Society of Glass Technology, Sheffield, UK, 2000, and “The Handbook of Glass Manufacture,” 3rd Ed. Vols. 1 & 2, by Fay Tooley (ed.), Ashlee Publishing Co. (New York), 1984, both incorporated herein by reference.
Conversion of one or more regenerator ports to oxy-fuel firing may be desired to retrofit the furnace to a hybrid furnace such as described in U.S. Pat. No. 6,519,973, incorporated herein by reference.
Terminating air-fuel firing and replacing energy input with oxy-fuel firing has its challenges. Since the furnace was initially designed as an air-fuel furnace, it is difficult to find suitable locations to place oxy-fuel burners. One location where oxy-fuel burners have been installed is in the port neck of the regenerator port.
The back of the port may be blocked off or otherwise obstructed to restrict or prevent flow of hot air from the regenerator into the port. A hole may be made in the top, bottom or sides of the port neck for the oxy-fuel burner installation. The oxy-fuel burner is then inserted through this hole and into the port neck. The oxy-fuel burner has to be designed to discharge fuel and oxygen into the furnace combustion space. This requires that the burner have an elbow or bend to change the direction of the flow of the fuel and oxidant. A problem with installing a burner through the port neck is that the size of the hole for inserting the burner is small in order to maintain the structural integrity of the port neck.
When the burner is installed through a hole in the top or bottom of the regenerator port neck, the burner will have a generally vertical section to convey the fuel and oxygen through the hole and a generally horizontal section to discharge the fuel and oxygen into the combustion space of the glass furnace with an elbow section between the generally vertical section and the generally horizontal section. When the burner is installed through a side wall of a regenerator port neck, the burner may have two generally horizontal sections with an elbow section between the two generally horizontal sections.
A problem with installing an oxy-fuel burner in the regenerator port neck is that the oxy-fuel burner will need to have the discharge nozzle close to the elbow section which requires an abrupt or marked change in the flow direction at a position close to the discharge nozzle. A long horizontal section terminating in the discharge nozzle within the port is problematic because of space limitations in the regenerator port. In addition, a long horizontal section terminating in the discharge nozzle is problematic because it would require a large hole cut in the wall of the port that may impact the structural steel surrounding the port. The abrupt or marked change in flow direction at a position close to the discharge nozzle causes high pressure drop, and turbulence of the flow leaving the nozzle. Turbulence causes rapid mixing and consequently combustion close to the nozzle resulting in short flames. Combustion close to the nozzle is undesirable because of nozzle overheating and, when the burner is used as a through-port burner, overheating of the refractory in the port neck.